1. Hiroshi Ishiguro Laboratories, Advanced Telecommunications Research Institute International, Soraku-gun, Japan
2. Guardian Robot Project, RIKEN, Soraku-gun, Japan
3. Graduate School of Informatics, Nagoya University, Nagoya, Japan
4. Graduate Faculty of Interdisciplinary Research, University of Yamanashi, Kofu, Japan
5. Graduate School of Engineering Science, Osaka University, Toyonaka, Japan